Combined thermodynamic and theoretical study on ether-functionalized ionic liquid mixture systems of [MOEmim][TFSI] with ACN/GBL

Abstract

Ether-functionalized ionic liquids (ILs) have a higher fluidity and are widely used in a variety of applications due to the introduction of the ether group. In order to better understand the relationship between properties and internal interactions of ether-based ILs, we prepared two ether-functionalized ILs 1–2-methoxyethyl-3-methylimidazolium bis((trifluoromethyl)sulfonyl)imide ([MOEmim][TFSI]) with acetonitrile (ACN) or γ-butyrolactone (GBL) mixture systems, and investigated the changes of their thermodynamic properties and internal interaction behaviors over the entire concentration range. First, the thermodynamic properties such as dynamic viscosity, density and electrical conductivity of the two mixture systems were measured from 288.15 K to 343.15 K. The excess molar volume (VE), and viscosity deviation (Δη) were calculated by using the measured experimental density and dynamic viscosity data, which can provide microscopic information on the interactions. Further, the intermolecular interactions of the mixture systems were evaluated by density functional theory (DFT) calculations. The sigma–profile (σ–profile) provided insight into the hydrogen bonds (H-bonds) and molecular surfaces interactions. We also used molecular dynamics simulations (MD) to study ILs mixtures in many different solvent concentrations, thereby providing a microscopic and macroscopic characterization of fluid structure, molecular aggregation, and intermolecular forces.